Conventionally, there is known an exhaust-gas purification device for reducing, in order to reduce NOx (nitrogen oxide) contained in exhaust gas from a ship engine or the like, NOx to nitrogen and water by using a selective reduction type NOx catalyst (SCR catalyst) and a reduction agent. For example, there is one that reduces NOx to nitrogen and water by generating ammonia from urea water injected into high temperature exhaust gas and causing the same to come into contact with a NOx catalyst.
It is known to provide, to such an exhaust-gas purification device, a mixer for mixing exhaust gas and a reduction agent together, in order to increase the efficiency of reduction action of the NOx catalyst. The exhaust-gas purification device increases the efficiency of exhaust gas reduction action by supplying, to the NOx catalyst, exhaust gas which has been forcibly mixed with a reduction agent by the mixer. For example, description is given in JP-A 2011-47293.
However, with the exhaust-gas purification device described in JP-A 2011-47293, an additive agent injection valve (injection nozzle) has to be disposed in such a way that an additive agent that is injected from the additive agent injection valve directly collides with the mixer. That is, the position of the mixer of the exhaust-gas purification device described in JP-A 2011-47293 with respect to the additive agent injection valve is restricted. Accordingly, depending on the routing of the exhaust pipe of an internal combustion engine, there is a problem that the additive agent injection valve and the mixer of the exhaust-gas purification device cannot be installed at appropriate positions.